1. Field of the Invention
The invention relates to crosslinkable compositions of silane-crosslinking prepolymers, to processes for preparing them, and to the use thereof as adhesives and sealants, especially for the adhesive bonding of substrates.
2. Description of the Related Art
Polymer systems which possess reactive alkoxysilyl groups are long-established. On contact with water or atmospheric moisture, even at room temperature, these alkoxysilane-terminated polymers are capable of undergoing condensation with one another, accompanied by elimination of the alkoxy groups. One of the most important applications of materials of this kind is the production of adhesives.
Adhesives based on alkoxysilane-crosslinking polymers, in the cured state, not only exhibit good adhesion properties on certain substrates, but also very good mechanical properties, having the capacity both for high tensile strength and high elasticity. A further key advantage of silane-crosslinking systems relative to numerous other adhesive and sealant technologies (e.g., relative to isocyanate-crosslinking systems) is the non-objectionable toxicological properties of the prepolymers.
There are many applications that prefer one-component systems (1K systems) which cure on contact with atmospheric moisture. The key advantages of one-component systems are, in particular, their very great ease of application, since in this case there is no need for the user to mix different adhesive components. In addition to the time/labor saving and the reliable avoidance of possible metering errors, there is also no need with one-component systems for the adhesive/sealant to be processed within a usually fairly narrow time window, as is the case with multicomponent systems after the two components have been thoroughly mixed.
One particular variant of adhesives based on alkoxysilane-crosslinking polymers is described in DE-A 10 2011 006130 and DE-A 10 2011 081264, comprising phenylsilicone resins as well as the silane-crosslinking polymers. The corresponding resin additives not only improve adhesion to numerous different substrates, but also—particularly in the case of the high resin contents described in DE 102011081264—lead to adhesives which, after full cure, exhibit considerably improved hardness and tensile shear strength.
A disadvantage of these systems, however, is the comparatively low elasticity of the corresponding resin-containing adhesive systems after they are cured. Thus the elongations at break with the systems described in the prior art are well below 200%. This is indeed not relevant for every application, but especially for elastic bonds, if, for example, materials having different thermal expansions are being surface-bonded to one another, the desire is for adhesives with high elasticity. This is also true of the surface bonding of wood, during the laying of wood flooring, for example, since woodbase materials expand and contract considerably depending on the atmospheric humidity.